Supported hydrogels, as well as hydrogels which act as carriers, are well-known in the art. Thus, e.g., acrylamide-N,N.sup.1 -methylenebisacrylamide was polymerized in a porous ceramic tube to form a permselective membrane composite useful for separating organic solvents from their water mixtures, as described in Chemical Abstracts, Vol. 113, No. 26, Abstract No. 233075v. In WO 8807075 there is described an enzyme reactor system composed of an enzyme entrapment hydrogel layer coated on a support and an ultraporous thin film membrane diffusion barrier.
In U.S. Pat. No. 4,668,654 there is described a hot or cold compress, comprising a layer of a substituted ureaurethane hydrogel material bonded to one side of a porous substrate, said hydrogel being formed from water, a polyol and a diisocyanate prepolymer. Similarly, in Japanese Patent 57119879, as abstracted in Chemical Abstracts, Vol. 98, No. 4, Abstract No. 1773j, there are described supported or self-supporting hydrogel polymer layers which were prepared using polymeric binders. For example, 2.0 kg ethylene-vinyl acetate copolymer in 8.0 kg PhMe was stirred with 2.0 kg powdered SGP polymer, to give a dispersion which was diluted with PhMe to a viscosity of 5 p and coated on a polyamide non-woven fabric.